There are a few hundred keter anomalies, and yet only about 10-20 got mentioned in Roget's 001 proposal. This is for SCPs that could possibly contain each other, some don't have to be keter.

I have some ideas, but I think the main one is that the 'Sheaf of Papers' could be flipped over and over, and the 'Database' horror writers would delete shitty articles, and has probably been going on for a long time.